Flooring



ug- 17, 1943- w. w. DoNELsoN ET AL 2,327,029

FLOORING Filed March 6, 1941 I @9224302115: Woazesow,

Zay MV1/UML Patented Aug. 17, 1941?v UNITED STATES PATENT GFFICE FLOORING William W. Donelson, Boston, Mass., and Richard L. Ahearn, White Plains, N. Y., assignors to Western Waterproong Company, Inc., Boston, Mass., a corporation o! New York Application March 6, 1941, Serial No. 382,008

' (ci. ca -c) 3 Claims.

This invention relates to flooring and more particularly to sparkproof flooring. It is known that heat sparks generated mechanically or electric sparks generated statically can and do cause serious explosions and damage when occurring in proximity to explosive compositions, and various constructions have been devised to combat this danger. Our invention is primarily concerned with this dangerin munition plants and elsewhere where a static electric spark or a heat spark generated by the dropping of a tool or the like onto the iioor can cause serious loss. It is appreciated that these two sources of sparks are largely responsible for such explosions and it'is one object of our invention to produce a new and improved sparkproof flooring which will positively eliminate this danger.

Our improved flooring embodies two primary elements namely (l) a iiooring material providing a flooring body and surface which meet the necessary requirements and which are nonproductive of heat sparks due to impact of other materials therewith and (2) a thin grid or the like of non-ferrous metal, which is conductive of electricity and non-productive of heat sparks due to impact of other materials, associated with the flooring, material and so distributed at its surface as to make contact with and draw off electric charges from persons, machines, equipment, or other elements in contact with the floor, the grid being suitably grounded whereby to dispose of static charges therefrom. It will be apparent that such combination produces a floor which eliminates the two dangers above recited.

The iiooring material-employed in our invenvtion is preferably of a composition containing magnesite and a further feature of the invention resides in the novel application of this composition to a sub-floor of concrete or the like in a manner maintaining the iiooring intact and preventing loosening and cracking thereof. Since magnesite flooring has considerable elasticity it `is applied over wood surfaces without serious danger of cracking but, due to this elasticity, it will crack when applied over sub-doors 'of concrete or the like which are substantially rigid and have a diii'erent coeiilcient of expansion from the top iiooring. The grid employed in our novel flooring serves to break the magnesite ilooring up into a plurality of independentunits which when bonded to a concrete subdescribed comprisesI the primary object of the invention. These features of the invention will be best understood and appreciated from the following description of a preferred embodiment thereof selected for purposes of illustration and shown in the accompanying drawing wherein,

Fig. 1 is a plan view, partially broken away, of our improved iiooring,

Fig. 2 is an enlarged sectional view taken on line 2-2 of Fig, l,

Fig. 3 is a fragmentary perspective view of a grid employed in the iooring.

The primary object of our invention is the production of a hoor which will eliminate the danger of sparks produced either statically or percussively and to that end we construct a top floor of material which is non-productive of sparks due to percussive contact or impact of other materials therewith, and we combine with this oor a grid of material conductive oi electricity and also non-productive of sparks due to percussive contact or impact of other materials therewith. The grid has portions thereof located in relatively close proximity to the top surface of the floor whereby to receive static charges of electricity from elements coming in contact with the top surface, the grid being suitably grounded to dispose of static electric charges therefrom. Both elements of the floor are sparkproof as far as impact of other materials therewith is concerned and the close proxlmity of the grid portions in the top floor is such as to contact and draw static charges from shoes of workmen, vehicles, machinery and other elements coming in contact with the floor where- 'by also eliminating sparks due to static charges.

In the drawing we have illustrated a sub-floor l0 of concrete on which rests a grid i2 comprising relatively thin strips I4 of non-ferrous metal such as copper, brass, aluminum,l etc. The strips are joined together at spaced points i6 to form a self-supporting grid structure having relatively small and adjacent openings i8 therebetween to the sub-floor. The top floor 20 comprises substantially independent units 22 of material nonproductive of sparks due to percussive contact or impact of other materials therewith, seated in the openings I8 and bonded to the sub-floor l0. While the units 22 can be of Wood or wood composition, suitable asphalt or asphaltic composition which is sparkproof from percussion or impact, or other materials possessing this characteristic, we prefer to employ a hardening cementitious composition and preferably one embodying magnesite. In forming the top floor we spread this composition over the grid and completely ll the openings I8. The units 22 thus formed or otherwise used are bonded to the subiioor and, after the composition comprising the I2 and this is ordinarily from M4 to 1/2".

top iioor has set. its top surface is `scraped or troweled to expose the grid i2. The grid vis sultably grounded to a water pipe or the like as indicated at 2d.

It will now be apparent that our improved ooring is sparkproof as far as electric and heat sparks are concerned. One particular object to be accomplished is the elimination of the danger of static sparks from workmen as they walk overr the floor and attention is particularly called to the fact that the grid i2 is not only exposed at the top surface of the iioor but the openings i8 are suiciently small to assure that some portion of the grid must always be contacted by a shoe in contact with the floor, whereby to receive static charges from the workmen and keep them free of danger from this source. Furthermore, both elements of the top floor being of materials which will not produce a spark by impact, danger from this source is also eliminated. Attention is also called to the fact that the improved ooring is composed primarily of iiooring compositions well known and in substantial and success-l ful use.

Magnesite ooring composition contains magnesite, magnesium chloride, soft fillers, and co1- oring matter, and its use and application to suboors is well known in the arts. It is of attractive appearance, dustless, easily cleaned, oil land grease proof and, due to a considerable amount of elasticity, it can be applied to wood sub-floors without danger of cracking. The application of magnesite composition to sub-oors of concrete, however, presents quite a diierent problem since concrete is substantially rigid and has a substantially different coecient of expansion from the magnesite flooring and for this reason the magnesite flooring in a relatively short time becomes loose and cracks. A further feature of our invention resides in the successful application of magnesiteA composition top flooring to a sub-floor of concrete, whereby stresses in the top iioor are so substantially eliminated that the iloor remains intact and free of cracking. The breaking up of our top i'loor 20 into a plurality of relatively small units 22 accomplishes this result since each unit is free to expand and contract without setting up stress in the other units and such independent action is not dependent upon the character of the sub-floor. Thus, even though the concrete sub-licor is quite rigid and of a coeii'lcient of expansion substantially differing from that of magnesite composition, the latter remains free of loosening or cracking since the independent units 22 can expand and contract normally without causing sucient stress in adjacent unitsto damage the oor. In other words, the invention so distributes and reduces the destructive stresses in the flooring as to eliminate the objections heretofore present.

It will be apparent that the thickness of the top floor I is determined by the depth of the grid It should furthermore be particularly pointed out that the units 22 comprise the main oor body 20, the grid strips i4 serving only the functions of (1) separating the top oor into relatively small units 22 and (2) receiving and carrying oi static charges of electricity. It is particularly pointed out that the strips I4 are preferably of very thin ribbon-like stock since such thin strips considerably reduce the cost of the oorlng and yet serve these functions to the fullest extent. In practice we have employed sixteen ounce sheet copper and other light and non-ferrous metals.

The strips le illustrated in the drawing are subw stantially heavier and thicker than we prefer to use, it being quite diiiicult to illustrate well such thin strips as we preferably employ. Grid ooring in present use employs a heavy grid together with a filler, the wear being taken almost solely by the grid, whereas our improved flooring employs a light and relatively inexpensive grid together with a filler adapted to take the wear, the grid not being depended upon for wear.

Having thus described our invention what we claim as new and desire to secure by Letters Patent of the United States is,

1. Sparkproof flooring, comprising the combination of a sub-oor, a composition top iloor thereon comprising homogeneous material nonproductive of sparks due to percussive impact of other materials therewith spread to uniform thickness over and bonded t the sub-floor, a grid of non-ferrous metal.nonproductive of sparks due to impact of other materials therewith resting on the sub-hoor and extending upwardly through the top oor to'a position approximating the top surface of the top floor whereby .to receive static charges of electricity from elements coming in contact with said top surface, and means grounding the grid whereby to dispose of static electric charges therefrom, the grid being highly conductive of electricity and having little weight-supporting strength and wear-resisting capacity per se and being molded into and supported by the top floor composition.

2. Sparkproof flooring comprising the combination of a sub-floor, a relatively hard composition top floor thereon containing magnesite and non-productive of sparks due to percussive impact of other materials therewith spread to uniform thickness over and bonded to the sub-oor, a grid of non-ferrous metal non-productive of sparks due to impact of other materials therewith associated with the top floor and having portions thereof located in relatively close proximity to the top surface of the top floor whereby to receive static charges of electricity from elements coming in Contact with said top surface, and means grounding the grid whereby to dispose of static electric charges therefrom, the grid being highly conductive of electricity and having little weightsupporting strength and wear-resisting capacity per se and being molded into and supported by the top floor composition.

3. Sparkproo ooring, comprising the combination of a sub-floor, a grid thereon of non-fer- :joined together at spaced points and shaped to form relatively small and adjacent openings therebetween to the sub-floor, a composition top oor on the sub-oor comprising hardening cementitious material non-productive of sparks due to percussive impact of other materials therewith spread to uniform thickness over and bonded to the sub-hoor, the top door being formed into independent units lling said openings in the grid and being of a thickness exposing the grid at the top surface thereof, and means grounding the grid whereby to dispose of static electric charges therefrom, the grid being highly conductive of electricity and having little weight-supporting strength and wear-resisting capacity per se and being molded into and supported by the top iioor composition.

WILLIAM W. DONELSON. I

RICHARD L. AHEARN 

